linux-kernel - Re: [PATCH v7 9/9] docs: ABI: testing: Document the Ampere Altra Family's SMpro sysfs interfaces

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Date:   Mon, 21 Mar 2022 11:03:25 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Quan Nguyen <quan@...amperecomputing.com>
Cc:     Lee Jones <lee.jones@...aro.org>, Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Jonathan Corbet <corbet@....net>,
        Derek Kiernan <derek.kiernan@...inx.com>,
        Dragan Cvetic <dragan.cvetic@...inx.com>,
        Arnd Bergmann <arnd@...db.de>,
        Thu Nguyen <thu@...amperecomputing.com>,
        Gustavo Pimentel <Gustavo.Pimentel@...opsys.com>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "open list:HARDWARE MONITORING" <linux-hwmon@...r.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        OpenBMC Maillist <openbmc@...ts.ozlabs.org>,
        Open Source Submission <patches@...erecomputing.com>,
        Phong Vo <phong@...amperecomputing.com>,
        "Thang Q . Nguyen" <thang@...amperecomputing.com>
Subject: Re: [PATCH v7 9/9] docs: ABI: testing: Document the Ampere Altra
 Family's SMpro sysfs interfaces

On Mon, Mar 21, 2022 at 04:46:36PM +0700, Quan Nguyen wrote:
> 
> 
> On 21/03/2022 15:23, Greg Kroah-Hartman wrote:
> > On Mon, Mar 21, 2022 at 03:13:55PM +0700, Quan Nguyen wrote:
> > > Add documentation for the Ampere(R)'s Altra(R) SMpro sysfs interfaces
> > > 
> > > Signed-off-by: Quan Nguyen <quan@...amperecomputing.com>
> > > ---
> > > Changes in v7:
> > >    + First introduce in v7     [Greg]
> > > 
> > >   .../sysfs-bus-platform-devices-ampere-smpro   | 133 ++++++++++++++++++
> > >   1 file changed, 133 insertions(+)
> > >   create mode 100644 Documentation/ABI/testing/sysfs-bus-platform-devices-ampere-smpro
> > > 
> > > diff --git a/Documentation/ABI/testing/sysfs-bus-platform-devices-ampere-smpro b/Documentation/ABI/testing/sysfs-bus-platform-devices-ampere-smpro
> > > new file mode 100644
> > > index 000000000000..9bfd8d6d0f71
> > > --- /dev/null
> > > +++ b/Documentation/ABI/testing/sysfs-bus-platform-devices-ampere-smpro
> > > @@ -0,0 +1,133 @@
> > > +What:		/sys/bus/platform/devices/smpro-errmon.*/errors_[core|mem|pcie|other]_[ce|ue]
> > 
> > Please split this out as one entry per file.
> > 
> 
> These sysfs share same format of HW errors (the 48-byte Arm vendor specific
> HW error record) but for separate HW domains: Core, PCIe, Mem... etc
> 
> > > +KernelVersion:	5.14
> > 
> > 5.14 is a long time ago.
> > 
> > > +Contact:	quan@...amperecomputing.com
> > > +Description:
> > > +		(RO) Contains the 48-byte Ampere (Vendor-Specific) Error Record, see [1]
> > > +		printed in hex format as below:
> > > +
> > > +		AA BB CCCC DDDDDDDD DDDDDDDDDDDDDDDD DDDDDDDDDDDDDDDD \
> > > +		   DDDDDDDDDDDDDDDD DDDDDDDDDDDDDDDD DDDDDDDDDDDDDDDD
> > > +		Where:
> > > +		  AA       : Error Type
> > > +		  BB       : Subtype
> > > +		  CCCC     : Instance
> > > +		  DDD...DDD: Similar to the Arm RAS standard error record
> > 
> > No, this is not a valid sysfs file, sorry.  This should just be one
> > value per file.
> > 
> 
> This 48-byte value is unable to separate into smaller values because it
> contain all information necessary to indicate a single HW error as per ARM
> RAS supplement document [1]. The format is to make it read-able other than a
> single 48-byte hex value.
> 
> [1] https://developer.arm.com/documentation/ddi0587/latest/

Just export the 48 byte hex value and make userspace split it up if it
wants to do so.  Don't do things in the kernel that can be done in
userspace.

thanks,

greg k-h